Sometimes having your period can be a pain — literally. Most girls have to deal with PMS, cramps, or headaches around the time of their periods. These problems are usually normal and nothing to worry about.

Here are the facts on which period problems are common and normal — and which ones might indicate there's something else going on.

What Is PMS?

Premenstrual syndrome (PMS) is the term for the physical and emotional symptoms that many girls and women get right before their periods begin each month. If you have PMS, you might experience:

acne

bloating

being very tired

backaches

sore breasts

headaches

constipation

diarrhea

food cravings

depression or feeling blue

irritability

mood swings

difficulty concentrating

problems handling stress

feeling tense

trouble sleeping

PMS is usually at its worst during the 1 to 2 weeks before a girl's period starts, and it usually disappears when her period begins.

Why Do Some Girls Get PMS?

Doctors have not pinpointed the exact cause of PMS, but many believe it is linked to changing hormone levels. Following a girl's period, the amounts of estrogen and progesterone (female hormones) in her body increase. Then about 1 week before her period starts, levels of both of these hormones begin to fall. The thinking is that these changing hormone levels can lead to PMS symptoms.

It isn't clear why some girls develop PMS and others don't. It's possible that those who develop PMS are simply more sensitive to the changes in hormone levels. There are other theories as well. For example, some believe that what you eat can affect how you feel, especially during the couple of weeks before your period.

Luckily, you can do a few things to ease PMS symptoms. Eating a balanced diet with lots of fresh fruits and vegetables and cutting back on processed foods like chips and crackers can help. You might also want to reduce your salt intake (salt can make you retain water and become more bloated) and, believe it or not, drink more water.

Say no to caffeine (it can make you jumpy and anxious) and yes to plenty of sleep. Getting enough calcium and taking a daily multivitamin can be helpful. Also, daily exercise and stress-relief techniques like meditation can help some girls.

When it comes to medicine, over-the-counter pain medicines like ibuprofen can relieve achy heads and backs. But for really serious PMS pain, see your doctor, who might be able to prescribe a different medicine or birth control pills to help.

Also let your doctor know right away if you feel very depressed or have had any thoughts of hurting yourself.

Why Do Some Girls Get Cramps?

Lots of girls have abdominal cramps during the first few days of their periods. Cramps are most likely caused by prostaglandins (pronounced: pross-tuh-GLAN-dinz), chemicals your body produces that make the muscles of the uterus contract. The good news is that cramps usually only last a few days. But if you're in pain, medicine like ibuprofen might help.

Exercise also can make you feel better, possibly because it releases endorphins, chemicals in the body that literally make you feel good. Soaking in a warm bath or putting a warm compress on your stomach won't make your cramps disappear but may help your muscles relax a little.

If you have severe cramps that keep you home from school or from doing stuff with your friends, or if over the counter medications aren't working, visit your doctor for advice.

Why Isn't My Period Regular?

It can take a few years from the time a girl starts menstruating for her body to develop a regular cycle. Even then, what's regular varies — girls' cycles can range from 21 to 45 days.

Changing hormone levels might make your period short one month (such as 2 or 3 days) and more drawn out (such as 7 days) the next. You might skip a month, get two periods almost right after each other, have a really heavy period, or one so light you almost don't notice it. (If you're sexually active and you skip a period, though, you should visit your doctor or a women's clinic to make sure you're not pregnant.)

All this irregularity can make planning for your period a real hassle. Try to keep track of when your last period started, and guess that about 4 weeks from that day you could be due for another. If you're worried about wearing that cute dress and suddenly starting your period at school, just make sure you pack protection. Carry a pad or tampon in your backpack, and wear a pantiliner to handle the first wave.

When it comes to periods, every girl's body has a unique (and unpredictable) timeline for getting on track. If your period still has not settled into a fairly predictable pattern after 3 years, or if you were having regular periods and then become irregular or have no period for a couple of months, make an appointment with your doctor to check for possible problems.

Why Haven't I Started My Period Yet?

Everybody goes through puberty at different speeds. Some girls begin menstruating as early as age 8 or 9; others don't get going until they're 15. It all depends on your hormones — and your family.

Want to guess when you'll get your period? Ask when your mom and grandmothers (from both sides of your family) started theirs. When you start puberty is partly linked to genetics. So although there's no guarantee that you'll follow in their footsteps, your relatives could give you a clue about your own period.

One thing that can delay puberty — and your period — is excessive exercising, usually distance running, ballet, or gymnastics, combined with a poor diet. For exercise to be excessive, it means more than just playing soccer a few times a week or working out once in a while with an exercise video. To exercise so much that you delay your period, you would have to train vigorously for several hours a day, most days of the week, and not get enough calories, vitamins, and minerals.

Unless compulsive exercise has postponed your period, there's nothing you can do on your own to hurry things along. If you haven't started to menstruate by the time you're 15, consult your doctor. He or she will examine you, and may do a pelvic exam and take a blood test to determine the hormone levels in your body. Different treatments are available depending on what is causing the delay in your period.

Even if it seems strange to you, most of the stuff that goes along with a girl's period is completely normal. But a few conditions can be more serious. If you suspect you have any of these problems, see your doctor for advice.

No Periods

Amenorrhea is the term doctors use for absence of periods. Girls who haven't started their periods by the time they are 15 may have primary amenorrhea, usually caused by a hormone imbalance or developmental problem.

There's also a condition called secondary amenorrhea, when a girl who had normal periods stops menstruating for at least 3 months. Low levels of gonadotropin-releasinghormone (GnRH) (pronounced: go-nad-uh-TROH-pin) , which controls ovulation and the menstrual cycle, frequently bring on amenorrhea.

Stress, anorexia, weight loss or gain, stopping birth control pills, thyroid conditions, and ovarian cysts are examples of things that can throw your hormones out of whack. To get everything back on course, your doctor may use hormone therapy.

If a medical condition is affecting your monthly cycles, treating that condition will help to fix the problem. As mentioned earlier, lots of strenuous exercise combined with a poor diet can also cause amenorrhea. Cutting back on exercise and eating a balanced diet with more calories will help correct the problem, but be sure to talk with your doctor too.

Heavy Periods

Abnormal uterine bleeding (AUB) is a term doctors use when talking about extremely heavy, long-lasting periods. Abnormal bleeding is more than just 1 or 2 days of a heavier-than-average flow. Girls who have AUB soak through at least a pad or tampon an hour for several hours in a row, have blood clots the size of a quarter or more, or have periods that are more than 7 days long. They may need to wear both a tampon and a pad at the same time, or may need to change tampons or pads overnight.

The most frequent cause of heavy bleeding is an imbalance between the amounts of estrogen and progesterone in the body. Because of this imbalance, the endometrium (pronounced: en-doh-MEE-tree-um), which is the lining of the uterus, keeps building up. Then when the body gets rid of the endometrium during a period, the bleeding is very heavy.

Many girls have hormone imbalances during puberty, so lots of girls have heavy bleeding. Other possible causes of heavy bleeding include thyroid conditions, bleeding disorders, or inflammation or infections in the vagina or cervix.

To help figure out the cause of abnormal bleeding, a doctor may do a pelvic exam, a Pap smear, blood tests, or an ultrasound. If doctors think heavy bleeding needs treatment, they will decide what to do based on what's causing the problem.

Extremely Painful Periods

Dysmenorrhea (pronounced: dis-meh-nuh-REE-uh) is the medical term for very painful periods. Primary dysmenorrhea — painful periods that are not caused by a disease or other condition — is more common in teens than secondary dysmenorrhea (painful periods caused by a disease or condition).

The culprit in primary dysmenorrhea is prostaglandin, the same naturally occurring chemical that causes cramps. Sometimes, prostaglandin can cause nausea, vomiting, headaches, backaches, diarrhea, and severe cramps when you have your period.

Fortunately, these symptoms usually only last for a day or two. Doctors usually prescribe anti-inflammatory medicines to treat primary dysmenorrhea. As with cramps, exercise, hot water bottles, and birth control pills might also bring some relief. Some of the more common conditions that can cause secondary dysmenorrhea include:

endometriosis, a condition in which tissue normally found only in the uterus starts to grow outside the uterus

fibroids or growths on the outside, inside, or in the wall of the uterus

For all of these conditions, you'll need a doctor to diagnose what's going on and then give you the treatment that's best for the problem you are having.

What to Do if You Suspect a Problem

When you have questions about your period or anything else related to your development, talk to your doctor. This is particularly true if you notice a change in your menstrual cycle. Though most period problems turn out to be nothing to worry about, it's always good to be safe.

See your doctor if:

You feel very depressed or hopeless, or have thought about hurting yourself. A severe form of PMS could cause this, and you should get help immediately.

You have not started your period by the time you are 15. The doctor can evaluate you to figure out why you haven’t gotten your period yet.

You stop getting your period or it becomes really irregular after it has been regular for several cycles. This can be a sign that you may have a hormone imbalance or a problem with nutrition.

You have very heavy or long periods, or get your period more often than every 21 days. Losing a lot of blood can cause anemia (low blood levels) and leave you feeling really weak and tired.

Your periods are really painful. The doctor can help figure out why your periods are painful, and treat you so that you are more comfortable.

Chances are that your painful or irregular periods are nothing to worry about. But if there is something going on, the quicker you get it taken care of, the sooner you'll be on your way to feeling great again.